Abstract

Major topics of great interest in neuroscience involve understanding thebrain function in stimuli coding, perceptive discrimination, and movementcontrol through neuronal activities. Many researchers are designing biophysicaland psychological experiments to study the activities of neurons in thepresence of various stimuli. People have also been trying to link the neural responsesto human perceptual and behavioral level. In addition, mathematicalmodels and neural networks have been developed to investigate how neuronsrespond and communicate with each other.In this thesis, my aim is to understand how the central nervous system performsdiscrimination tasks and achieves precise control of movement, usingnoisy neural signals. I have studied, both through experimental and modellingapproaches, how neurons respond to external stimuli. I worked in three aspectsin details. The first is the neuronal coding mechanism of input stimuliwith different temporal frequencies. Intracellular recordings of single neuronswere performed with patch-clamp techniques to study the neural activitiesin rats somatosensory cortices in vitro, and the simplest possible neural model—integrate-and-fire model—was used to simulate the observations.The results obtained from the simulation were very consistent with that in theexperiments. Another focus of this work is the link between the psychophysicalresponse and its simultaneous neural discharges. I derived that under awidely accepted psychophysical law (Weber’s law), the neural activities wereless variable than a Poisson process (which is often used to describe the neuronspiking process). My work shows how psychophysical behaviour reflectsintrinsic neural activities quantitatively. Finally, the focus is on the controlof movements by neural signals. A generalized approach to solve optimalmovement control problems is proposed in my work, where pulses are usedas neural signals to achieve a precise control. The simulation results clearlyillustrate the advantage of this generalized control.In this thesis, I have raised novel, insightful yet simple approaches to studyand explain the underlying mechanism behind the complexity of neural system,from three examples on sensory discrimination and neural movementcontrol.